Encoding and Hashing

Executive Summary

Encoding transforms data into another representation. Hashing produces a fixed-length fingerprint of data. Encryption protects data with a key.

This cheatsheet is for quick lookup when handling files, payloads, hashes, certificates, tokens, and encoded strings.

Encoding vs Hashing vs Encryption

Concept	Reversible	Key Required	Common Use
Encoding	Yes	No	Data formatting and transport
Hashing	No	No	Integrity checks and password storage
Encryption	Yes	Yes	Confidentiality

Base64

Encode a file:

base64 file.bin > file.b64

Encode without line wrapping:

base64 -w 0 file.bin

Decode:

base64 -d file.b64 > file.bin

Encode a string:

echo -n "text" | base64

Decode a string:

echo "dGV4dA==" | base64 -d

PowerShell encode:

[Convert]::ToBase64String([Text.Encoding]::UTF8.GetBytes("text"))

PowerShell decode:

[Text.Encoding]::UTF8.GetString([Convert]::FromBase64String("dGV4dA=="))

Hex

String to hex:

echo -n "text" | xxd -p

Hex to string:

echo "74657874" | xxd -r -p

Hex dump a file:

xxd file.bin

URL Encoding

URL encode with Python:

python3 -c 'import urllib.parse; print(urllib.parse.quote("admin@test.com"))'

URL decode with Python:

python3 -c 'import urllib.parse; print(urllib.parse.unquote("admin%40test.com"))'

Common characters:

Character	Encoded
Space	`%20`
`"`	`%22`
`#`	`%23`
`%`	`%25`
`&`	`%26`
`'`	`%27`
`/`	`%2F`
`:`	`%3A`
`=`	`%3D`
`?`	`%3F`
`@`	`%40`

Hashing Files

MD5:

md5sum file.bin

SHA1:

sha1sum file.bin

SHA256:

sha256sum file.bin

SHA512:

sha512sum file.bin

PowerShell hash:

Get-FileHash .\file.bin -Algorithm SHA256

Hashing Strings

MD5:

echo -n "password" | md5sum

SHA256:

echo -n "password" | sha256sum

Python SHA256:

python3 -c 'import hashlib; print(hashlib.sha256(b"password").hexdigest())'

Identify Hash Lengths

Hash	Hex Length
MD5	32
SHA1	40
SHA256	64
SHA512	128
NTLM	32
bcrypt	Variable, often starts with $2a$ , $2b$ , or $2y$
SHA-crypt	Starts with $5$ or $6$

Common Password Hash Indicators

Format	Meaning
$1$	MD5-crypt
$2a$ , $2b$ , $2y$	bcrypt
$5$	SHA256-crypt
$6$	SHA512-crypt
$krb5asrep$	Kerberos AS-REP hash
$krb5tgs$	Kerberos TGS hash
`aad3b435b51404eeaad3b435b51404ee`	Empty LM hash
32 hex chars	Could be MD5 or NTLM

OpenSSL Encryption

Encrypt file:

openssl enc -aes256 -pbkdf2 -iter 100000 -in file.txt -out file.enc

Decrypt file:

openssl enc -d -aes256 -pbkdf2 -iter 100000 -in file.enc -out file.txt

Generate random bytes:

openssl rand -hex 16

Generate random base64:

openssl rand -base64 32

Certificates

View certificate details:

openssl x509 -in cert.pem -text -noout

Check remote TLS certificate:

openssl s_client -connect example.com:443

Show certificate dates:

echo | openssl s_client -connect example.com:443 2>/dev/null | openssl x509 -noout -dates

Show certificate subject:

echo | openssl s_client -connect example.com:443 2>/dev/null | openssl x509 -noout -subject -issuer

JWT Quick Checks

JWTs usually have three dot-separated parts:

header.payload.signature

Decode JWT header:

echo 'HEADER_PART' | base64 -d

Decode JWT payload:

echo 'PAYLOAD_PART' | base64 -d

If padding is missing, add = characters until decoding works.

File Integrity Workflow

Step	Command
Hash original	`sha256sum file.bin`
Transfer file	Use chosen transfer method
Hash received copy	`sha256sum file.bin`
Compare hashes	Hashes should match exactly

Notes

Base64 is not encryption.
Hashes are not reversible.
Fast hashes like MD5 and SHA1 are weak for password storage.
Use SHA256 or stronger for integrity checks.
Use authenticated encryption or trusted secure transfer methods for sensitive data.